"We have registered an FIR against Mr Baitha on Sunday on the basis of a complaint by Moh Ansari of Dharampur village, who lost five grandchildren in the tragedy on Saturday," Station House Officer of Meenapur police station Sona Prasad Singh said.
Mr Singh said raids were conducted to arrest the BJP leader who hails from Sitamarhi district but he is absconding. On Sunday, shocked villagers staged a protest by blocking the National Highway to demand his arrest.
Mr Ansari said in his police statement that Mr Baitha was driving the vehicle when the speeding vehicle run over the children on Saturday. Clad in a white cotton kurta-pyjama, he fled after the vehicle hit and killed the school children, he added.
Mr Ansari said a closed-circuit television footage also showed the BJP leader driving the vehicle.
The accident occurred near Dharampur school on National Highway-77 in Minapur block when a Balero jeep hit the children while they were crossing the road. Angry over the deaths, area residents beat up teachers and set ablaze chairs and benches there on Saturday.
The state has announced Rs 4 lakh each to the next of kin of the killed children.
Opposition Rashtriya Janata Dal has already demanded stern action against the culprit.
Leader of Opposition Tejashwi Yadav, after visiting the injured, said their families told him that the killer vehicle belonged to the BJP leader and no arrest had been made so far.
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